Zeolite has regularly arranged micro pores and in general resists heat and chemicals, and therefore, it is used in various fields. Zeolite, which is alumino silicate having part of Si replaced with Al, has pores of a molecular order (about 0.3 to 1 nm) of oxygen 8- to 14-membered ring and has a stereoselective adsorption ability. Therefore, zeolite is widely used in the fields of, e.g., liquid separation, vapor separation, gas separation, membrane reactors, solid acid catalysts, separation adsorbents, and ion exchangers. The membrane separation method using a zeolite membrane has recently been proposed and employed in place of the distillation method which requires much heat energy for separation and collection of organic compounds from a mixture containing the organic compounds.
Zeolite is ordinarily produced by hydrothermal synthesis, in which an aluminum source, a silica source, an alkali metal, and an organic template such as an amine are added to a large amount of water, so as to achieve the target zeolite composition, the resulting mixture is placed in a pressure container such as an autoclave along with a porous support, the pressure container is sealed, and then the mixture is heated, thereby to synthesize a zeolite membrane on the support. The support is constituted by alumina, mullite, a porous metal, Vycor glass, etc. which may have seed crystals adhered thereto.
For example, Patent Literature 1 discloses a method for forming a zeolite membrane having the CHA crystal structure on a porous support by hydrothermal synthesis, using an aqueous reaction mixture including a Si element source, an Al element source, an alkali source including potassium, and 1-adamantine amine derivative as an organic template.
However, when the zeolite membrane having the CHA crystal structure obtained by this method is used as a separation membrane to separate and collect, e.g., acetic acid or 2-propanol from a mixture of water and acetic acid or a mixture of water and 2-propanol, respectively, the permeation flux (the mass of the permeating substance per unit time or unit area) is low and the throughput is small, and therefore, the separation takes a long time.